High molecular weight fatty acids



Patented Sept. 11, 1951 UNITED STATES PATENT OFFICE HIGH MOLECULAR WEIGHT FATTY ACIDS No Drawing. Application August 27, 1947, Serial No. 770.949

12 Claims.

This invention relates to a method for stabilizing and improving the color of fatty acids. The invention more particularly relates to the treatment of high molecular weight fatty acids in such manner as to remove from them, and/or to render inactive in them, substances which are capable of imparting undesirable color and/or rancidity to soaps or other products made up from the fatty acids, these substances being sometimes referred to hereinafter for convenience and brevity as latent color bodies." The invention also relates to improved fatty acids that have been treated in the manner and for the purposes indicated more particularly hereinafter.

Relatively high molecular weight fatty acids frequently contain small amounts of polyoleflnic compounds such as linoleic and linolenic acids and possibly other compounds containing two or more double bonds per molecule. These polyolefinic compounds are particularly undesirable where the high molecular weight fatty acids contaminated therewith are to be exposed under conditions of use to oxidizing conditions, since these polyolefinic contaminants are converted to undesirable peroxides comparatively readily. In certain instances undesirable mono-oleflnic contaminants may also be present, and these too are substantially completely removed by the process of the present invention. In any event, when the high molecular weight fatty acids containing undesirable unsaturated contaminants of the nature indicated are thereafter employed in the manufacture of soap or other cosmetic products, the resulting products frequently possess or acquire an undesirable yellow color due to the formation of alkali derivative of keto hydroxy acids.

It has been proposed to eliminate insofar as possible difliculties of this nature by pretreating the higher molecular weight fatty acids by various methods prior to convertingisame into the final soap or other products. Fan-instance, it has been proposed to stabilize fatty acids by subjecting them to selective hydrogenation, by subjecting them to bleaching treatment with a suitable contact material such as activated clay in particle form, and by various other methods known in the technical literature. However, while such methods may be to some degree satisfactory for the intended purpose, each one possesses one or more serious disadvantages, such as inordinately high cost, the necessity for using hydrogenation catalysts or other contact materials in subdivided form which requires a costly separate filtering operation. a failure to effect anything like complete and permanent removal of the undesired latent color bodies, and perhaps others which would show up during any attempt to practice on a commercial scale any of the previously proposed methods.

It is accordingly an object of the present invention to provide a simple process for treating high molecular weight fatty acids for the purpose of stabilizing them against the formation of rancidity and/or for improving their color, as well as similarly stabilizing and/or improving the color of soaps or other products for which they are used as intermediates.

It is a further object of the invention to provide a process for treating high molecular weight fatty acids in such manner as substantially to inactivate any relatively small proportion of latent rancidityand/or color-forming bodies that may be present therein, and either with or without subsequent removal of the inactivated contaminants, prior to employing said high molecular weight fatty acids for the manufacture of soaps or other useful products.

In accordance with the present invention it has been discovered that high molecular weight fatty acids, such for example as those intended for use in manufacturing soaps or other cosmetic products, are very greatly improved with respect to freeing them from contaminants which give rise to undesired rancidity and/or color, either directly in the high molecular weight fatty acids themselves or subsequently in the soap or other products made therefrom, by .pretreatingv the high molecular weight fatty acids at an elevated temperature with a relatively small amount of an aliphatic acid anhydride having an alphabeta-enal group, preferably maleic anhydride, in conjunction with a relatively small amount of a suitable catalyst. It has been discovered that under these conditions the acid anhydride preferentially reacts with the olefinic or polyolefinic contaminants normally present in small proportions even in what are ordinarily regarded as rather refined grades of high molecular weight fatty acids, to form high molecular weight resinous or condensation products which are inert and/or relatively more stable and which, if desired, can be readily removed from the high molecular weight fatty acids by methods such as filtration or distillation. The presence of the catalyst promotes the reaction between the acid anhydride and the unsaturated contaminants. It has also been found that it is not necessary invariably to remove the high molecular weight resins or condensation products formed in this manner and that, on the contrary, the high molecular weight fatty acids which contain such resins or condensation products as a result of a pretreatment of the nature indicated may be made up directly into soaps or other useful products, the final products bein uite satisfactory for commercial use despite the presence therein of small proportions of resinous or condensation products of the character mentioned.

In a copending application Serial No. 770,950, filed August 27, 1947, by John Ross, there has been described and claimed a process involving a. pretreatment of high molecular weight fatty acids, esters andoils with acid anhydride alone. While in the case of high molecular weight fatty acids a pretreatment with maleic anhydride alone generally gives very desirable results, the present invention represents a still further improvement in the treatment of materials of the last-mentioned kind.

The treatment or pretreatment with maleic anhydride and catalyst in accordance with the present invention is conducted at elevated temperatures of the order of 150 to 300 C., with temperatures in the range of approximately 160 to 225 C. representing preferred temperature conditions. Especially desirable results have been obtained with temperatures in the range of about 180 to 200 C.

The quantity of maleic anhydride to be employed in the treatment according to the present invention may be varied from scarcelymore than a trace up to approximately 7% by weight of the fatty acid undergoing treatment, depending upon the degree of contamination thereof. Generally speaking, from about i to about will be found to be very satisfactory. It will be appreciated that a slight excess of maleic anhydride is preferably employed, such slight excess doing no harm if permitted to remain permanently in the fatty acid undergoing treatment. The optimum quantity necessary for any particular batch of fatty acid undergoing treatment may be readily determined by one or a few trial treatments of small aliquots in order to obtain a quantitative idea of the degree of contamination encountered, and hence the quantity of maleic anhydride required. In those cases where the difference between the iodine and thiocyanogen values of the fatty material to be treated is a measure of polyunsaturated constituents present, these values may be used to compute the minimum amount of maleic anhydride required.

In accordance with the present invention, in conjunction with the maleic anhydride there is employed a relatively small proportion of a suitable catalyst for promoting the reaction between the maleic anhydride and the unsaturated contaminants present in the fatty acid undergoing treatment. As suitable catalysts there may be mentioned mineral acids such as sulphuric acid, hydrochloric acid or a phosphoric acid, particularly orthophosphoric acid. Organic acid peroxides such as stearyl peroxide, benzoyl peroxide and acetyl peroxide are also excellently adapted for use in the present process.

The quantity of catalyst may vary from traces up to approximately 2% based upon the weight of the fatty acid undergoing treatment.

The reaction time may vary over wide limits, it being only necessary to afford sufficient time to insure substantially complete reaction between the maleic anhydride and the contaminants present in the fatty acid undergoing treatment. Reaction times varying from about 30 minutes to about 3 hours have been found to be satisfactory. Particularly satisfactory results have been obtained in actual practice with reaction times of approximately one hour.

The process may be carried out batchwise or in a continuous manner, the latter being particularly desirable when processing large quantitles of high molecular weight fatty acids in accordance with the present invention.

If the resins or condensation products formed by reaction between the maleic anhydride and the olefinic or polyolefinic contaminant are to be removed, this may be done by filtration or distillation, the purified acids being taken overhead in vapor phase leaving the resins or condensation products behind as non-volatile residues.

In order to assist in the better understanding of this invention, but without thereby intending to limit its scope, the following examples are set forth by way of illustration. Unless otherwise specified, all parts represent parts by weight.

Example I A quantity of fatty acids derived from tallow, and consisting chiefly of stearic, palmitic and ole'ic, with some linoleic, .linolenic and other polyunsaturated acids, wa heated with 3.0% of maleic anhydride and a trace of sulphuric acid at l60-190 C. for a period of one hour, followed by distillation, resulting in a, mixture of fatty acids of which the color stability had been increased approximately 10 to 15 times over that of the corresponding untreated fatty acids. The maleic anhydride treatment appreciably increased the amount of still residue left from the distillation operation, giving 87-90% overhead, as contrasted with the usual 93-98% obtained in the absence of such pretreatment.

By way of explanation of the general manner in which the, degree of improvement in this and the succeeding examples was determined, it may be stated that the procedure was as follows: A sample of overhead, obtained by distillation of the treated material, was placed in an oven and held at 70 0., portions being removed at suitable interval of time. The portions so removed were dissolved in methanol, 50 Baum sodium hydroxide was added, the mixture was heated and the color observed visually. Aging of the overhead product obtained from the treated material was continued until a slightly yellow color was obtained upon adding the caustic. The time of aging under these conditions, as compared with the time of aging of the overhead product obtained from an otherwise similar material that was not treated with maleic anhydride plus catalyst, was taken as a measure of the degree of stabilization obtained by the maleic anhydride-catalyst treatment.

Example II Example 111 In order to provide a control, a portion of tallow fatty acids identical with that employed in Example I was treated exactly in the manner there indicated, but without the addition of maleic anhydride and sulphuric acid. This control showed discoloration in two hours.

Example IV This was a duplicate of Example II, except that the treatment was applied to a different batch of tallow fatty acids. The treated material showed discoloration in 43 hours.

Example V This was a duplicate of Example IV, except that 0.5% of stearyl peroxide was employed as catalyst and the temperatures were slightly higher, namely 160-200 C. The treated mate rial showed discoloration in 26 hours.

Example VI The procedure of the present invention is also especially applicable to the treatment of red oil (commercial oleic acid, which may contain for example about linoleic acid). For example, three portions of red oil (white olein-Gross) were treated by the procedure set forth above in Example I except that one portion was admixed with 7% of maleic anhydride and a trace of sulphuric acid as catalyst, the second was admixed with 7% of maleic anhydride and the third (untreated) was used as a control. The aging times for the three portions were 53 hours, 48 hours and 4 hours respectively.

It will be apparent from the foregoing that the present invention contemplates a process for the pretreatment of high molecular weight fatty acids that is particularly well adapted for stab'ilizing and/or improving the color-.properties of such materials when contaminated'with small proportions of colorand/or rancidity-imparting bodies such as oleflnic or polyolefinic compounds normally present as contaminants even in what would otherwise be regarded as highly refined materials of this nature. After pretreatment in the manner indicated herein, the high molecular weight fatty acids are. found to be greatly improved in the respects noted, the improvement being Of 8 permanent nature and carrying 0V6! even into the final soap-or other products that are manufactured from the high molecular weight fatty acids so treated.

While'maleic anhydride has been used to describe and illustrate the invention, other aliphatic acid anhydrides having an alpha-beta-enal group may be substituted with comparable results. Buch anhydrides preferably have up to about 7 carbon atoms per molecule, and include fumaric. acrylic, crotonic, itaconic, citraconic, etc. and their homoioss and analogs. The-corresponding acids, and esters thereof, maybe employed as full equivalents of the anhydrides and therefore the use of the acid or ester form isregarded as falling within the scope of the claims.

Where reference is made in the present specification and claims to the treatment offlhish.

molecular weight fatty acids, it is to be understood that this refers to the fatty. acids containing from 8 to 24 and particularly from 12 i018 carbon atoms per molecule.

I am aware that numerous variations in the proceduresdescribedebovemaybemedewithout presence of a catalyst for said reaction, and t'erminating the treatment when said polyolefinic compounds have reacted with said anhydride andbefore a substantial amount of monooleflnic acids have reacted therewith.

2. A method as set forth in claim 1 in which said elevated temperature is within the range of 150 to 300 C..

3. A method as set forth in claim 1 in which said anhydride is maleic anhydride. 1

4. A method as set forth in claim 1 in which the catalyst is a mineral acid.

5. A method as set forth in claim 1 in which the catalyst is an organic acid peroxide.

6. A method as set forth in claim 1 in which the catalyst is present in an amount up to about 2%.

7. A method as set forth in claim 3 in which the maleic anhydride is used in an amount up to 7%.

8. A method as set forth in claim 2 in which the time of treatment is within the range of 30 minutes to 3 hours.

9. A method as setforth in claim '4 in which the mineral acid issulphuric' acid.

10. A method as set forth in claim 5 in which I the organic acid peroxide is stearyl peroxide.

11. A method of stabilizing oieic acid which comprises heating impure oleic acid at about to 300 C. with maleic anhydride from an effective amount up to about 7% by weight of said which comprises treating an impure oleic acid at about 150 to 300. C. for about 30 minutes to 3 hours with a trace to 7% 'of maleic anhydride in the presence of a trace to 2% of a catalyst for the reaction of maleic anhydride with polyunsaturated compounds. and separating, oieic acid from the reaction mixture by distillation.

WALTER aosssru. ram.

BEFEitENCES crrsn The following references are of record in the fiie of this patent:

UNITED s' 'rs'rss PATENTS Number Name Date 2,188,882 clocker Jan. 30, 1940 

1. A METHOD OF STABILIZING FATTY ACIDS WHICH COMPRISES TREATING FATTY ACIDS CONTAINING MINOR AMOUNTS OF POLYOLEFINIC COMPOUNDS AT ELEVATED TEMPERATURE WITH AN ACID ANHYDRIDE HAVING AN ALPHA-BETA-ENAL GROUP IN SUFFICIENT AMOUNT TO REACT WITH SID POLYOLEFINIC COMPOUNDS AND IN THE PRESENCE OF A CATALYST FOR SAID REACTION, AND TERMINATING THE TREATMENT WHEN SAID POLYOLEFINIC COMPOUNDS HAVE REACTED WITH SAID ANHYDRIDE AND BEFORE A SUBSTANTIAL AMOUNT OF MONOOLEFINIC ACIDS HAVE REACTED THEREWITH. 